help us out. >> the brits are particular. but, we're at selfridges, one of the best stores in the country, to help us out. >> reporter: let's go. nick wasn't kidding. inside the high-end department store, i found out from fashion expert, sophie, that dressing for a royal wedding is no easy matter. so, which dresses do you think i should try on? because the wedding will take place at westminster abbey, sleeves for women are a do. and this would take care of the sleeveless problem. looking too sexy is a don't. >> quite sexy for a royal wedding. i have to be honest. >> reporter: and while it's important to look proper, it's not good to look stuffy. i can't tell if i like it. or if i look like a doily. what do you think? decisions, decisions, decisions. >> so, the invitation says uniform. dressing for men, that's even trickier. according to the royal wedding invitation, men are required to wear one of three kinds of dress. a military uniform. or for us civilians, a morning coat or lounge suit. a lounge suit isn't exactly as casua